Clay-thickened grease containing synergistic additive combination

ABSTRACT

Clay-Thickened grease containing synergistic proportions of zinc dialkylnaphthalene sulfonate, an ester of an aliphatic monohydric alcohol and an aliphatic monocarboxylic acid, and zinc napththenate.

United States Patent [1 1 Gannon et a1.

54 CLAY-THICKENED GREASE CONTAINING SYNERGISTIC ADDITIVE co pl o [75] Inventors: Joseph A. Gannon, New Orleans;

Richard L. Deck, Metairie, both I .22 La [52] US. Cl 252/21, 252/28, 252/389, 252/400 [51] Int. Cl. Cl0m 5/22, ClOm 5/14 [58] Field of Search 252/21, 28, 389,

[56] References Cited UNITED STATES PATENTS 2/1968 Caruso 252/21 1/1964 Rees et al. 252/21 Oct. 2, 1973 3,539,512 11/1970 Rohde et al. 252/21 2,764,548 9/1956 King et al. 252/21 2,487,261 11/1949 Zimmer et al. 252121 2,434,539 1/1948 Beerbower et a1 252/21 OTHER PUBLICATIONS Polar-Type Rivet Inhibitors by- Baker et 211., Pages 2338-2346, Industrial & Engineering Chem., Vol. 40, No. 12, 1948.

Primary Examiner-Patrick P. Garvin Assistant Examiner-l. Vaughn Attorney-Glen R. Grunewald and John H. Colvin [571 I ABSTRACT Clay-Thickened grease containing synergistic propor- Q tions of zinc dialkylnapththalene sulfonate, an ester of an aliphatic monohydric alcohol and an aliphatic me e e qxx i 1 and. zin r a t le 5 Claims, No Drawings CLAY-THICKENED GREASE CONTAINING SYNERGISTIC ADDITIVE' coMEINA rIoN BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to clay-thickened lubricating grease compositions containing a unique combination of additives which impart significantly improved properties to the grease in a number of important aspects.

2. Discussion of the Prior Art It is well known in the art that greases of exceptionally high mechanical stability and melting point can be prepared from mineral and/or synthetic oils thickened with waterproofed clay gelling agents. Such products have found widespread use particularly in applications wherein high temperatures or other adverse conditions are encountered, e.g., in steel rolling mills wherein lubricating greases are subjected to a combination of high temperature, dust, heavy loads and water contamination. To perform adequately under such conditions, the lubricating grease employed must be resistant to the degradative effects of water, be oxidation resistant and have good load carrying properties. In addition, it is desirable that the grease inhibit corrosion and have good lubricity, thermal stability and dispensability properties. Corrosion inhibition properties are required because of the presence of water in the lubricatingenvironment, while good dispensability, i.e., pumpability, properties are necessary because of the increasingly common use of centralized lubricant distributing systems in steel mills and other industrial plants. Such systems necessitate transferral of the grease over considerable distances, often at varied temperatures, thus requiring a product that is readily pumped but which must still have a sufficiently high consistency to act as a seal against the entry of dirt. Lubricity and thermal stability are particularly important in applications such as the lubrication of bearings on rolling mill equipment which generally are subjected to enormous pressures at very high temperatures because of contact of the rolls with the heated metal.

While numerous additives and additive combinations have been proposed to improve the load carrying and antioxidant properties of clay-thickened greases, these prior art formulations by-and-large have proved deficient in one or more of the other above-mentioned properties. The present invention provides grease compositions which not only possess excellent mechanical and oxidative stability and load carrying capacity, but additionally exhibit unexpectedly improved anticorrosion, lubricity, thermal stability and dispensability properties as well.

SUMMARY OF THE INVENTION It has now been found that grease compositions consisting essentially of a major amount of lubricating oil gelled to grease consistency by means of a waterproofed clay having incorporated therein (1) a zinc di-C, to C alkyl naphthalene sulfonate, (2) an ester of a C to C aliphatic monocarboxylic acid and a C, to C, aliphatic monohydric alcohol and (3) zinc naphthenate, have substantially improved properties in respect to corrosion inhibition, lubricity, thermal stability and dispensability. The remarkable effectiveness of the present compositions is believed due to a cooperative effect between the aforementioned additives, which produces a composition having properties markedly superior to those containing the additives individually. Because of these significantly improved properties, the inventive greases are useful in a variety of applications such as satisfying the diverse lubricating requirements of steel rolling mills and other industrial plants, particularly those employing centralized lubrication systems.

DESCRIPTION OF PREFERRED EMBODIMENTS The zinc dialkyl naphthalene sulfonates employed in the improved compositions of the invention are those having two alike or dissimilar alkyl substituents of four to 12 carbon atoms on the naphthalene ring. Such compounds can be prepared by alkylating naphthalene with highly branched olefins, e.g., nonenes, using a suitable catalyst such as aluminum chloride or hydrogen fluoride, followed by reaction with sulfuric acid to form an alkylnaphthalene sulfonic acid which is then reacted I with zinc oxide, hydroxide or carbonate to form the zinc salt. A detailed description of this method of preparation can be found in US. Pat. No. 2,764,548 to King et al. A particularly advantageous compound of the aforementioned type is zinc dinonyl naphthalene sulfonate which is sold commercially in a solvent under the trade name NA-SUL ZS. The zinc dialkyl naphthalene sulfonate component can be employed in the present compositions in concentrations of 0.01 to 3.0 percent by weight with concentrations of 0.1 to 1.5 percent by weight generally being sufficient to impart the desired properties to the inventive compositions. All concentrations recited in the specification and claims, unless otherwise specified, refer to percent by weight basis of the total grease composition.

The esters which can be used in accordance with the invention are esters of C to C aliphatic monocarboxylic acids and C, to C, aliphatic alcohols. These esters generally correspond to formula wherein R, is an aliphatic group of 12 to 24 carbon atoms and R is an aliphatic group of one to eight carbon atoms. Esters formed from normal saturated aliphatic acids and alcohols are preferred, especially esters of C to C aliphatic monocarboxylic acids, e.g., palmitic or stearic acids with C, to C aliphatic monohydric alcohols. Butyl stearate has been found to be particularly effective in the compositions of the invention. The aforementioned esters can be suitably employed in concentrations of 0.1 to 5 percent by weight, with concentrations in the range of from 0.5 to 2.0 percent by weight being particularly preferred.

The zinc naphthenate component of the present additive combination and its method of preparation are well known in the art. Generally such additives are prepared by reacting a zinc compound, e.g., zinc oxide, with naphthenic acids such as those obtained from certain American crudes, especially those obtained from California crudes. Naphthenic acids are typically obtained as mixtures having an average molecular weight of 250 or higher, for example, from 250-1,000. The proportion of zinc in the zinc naphthenate additive is on the order of 9.0 to l 1.0 percent by weight basis of the additive. The zinc naphthanate additive is employed in the present grease compositions in concentrations of 0.1 to 5.0 percent, preferably 1.0 to 3.0 percent by weight.

The preferred thickening agents for use in the present compositions are hydrophobic clays. Such thickening agents can be prepared from clays which are initially hydrophilic in character, but which have been converted into a hydrophobic condition by treatment with a hydrophobic surface active agent. Clays having a base exchange capacity of at least 25 milliequivalents per 100 grams, preferably between 25 and 100 milliequivalents per 100 grams, are very suitable for conversion into the desired thickening agents, particularly montmorillonites such as bentonite, hectorite and saponite. Other clays such as sepiolite, biotite, attapulgite, illite, vermiculite, zeolite and the like are also suitable. Of the foregoing, bentonite and hectorite clays are preferred, particularly hectorite. The amount of clay thickener employed in the present compositions will vary depending on the consistency desired. In general, clay thickener concentrations of 2.0 to 25.0 percent by weight can be employed, with concentrations of 5.0 to 15.0 percent by weight being preferred.

The surface active agents used to convert the clays to a hydrophobic condition can be either cationic, anionic or non-ionic, but preferably are cationic in character and can be either adsorbed on the surfaces of or reacted with the clay. Such hydrophobic surface active agents are well known in the art and are described, for example, in U.S. Pat. Nos. 2,554,222 and 2,623,853 issued to Stross, U.S. Pat. No. 2,623,852 issued to Peterson, and in U.S. Pat. No. 2,531,440 issued to Jordan. The surface active agent will normally be utilized in an amount sufficient to waterproof" the clay, i.e., enable the clay to maintain a grease structure even when the grease becomes contaminated with water. Generally, surface active agent concentrations of from 2.5 to 5 percent by weight of the total composition will be sufficient to accomplish this purpose.

A class of surface agents which produce hydrophobic clays particularly suitable for use in the inventive compositions are aminoamides of polyalkylene polyamines, preferably formed between fatty acids having to 20 carbon atoms per molecule and a mixture of polyethylene polyamines comprising 20-80 percent by weight diethylene triamine, the remaining fraction being polyethylene polyamines having an average molecular weight of 220-450. Such aminoamides can be prepared by reacting 70-25 percent by weight of the fatty acids with 30-75 percent by weight polyalkylene polyamines at 200-225 C for a period of l to 4 hrs. The preferred aminoamide waterproofing agents and their methods of preparation are fully described in U.S. Pat. No. 3,050,463 issued to Peterson.

The major component of the present compositions is a lubricating oil which can be any oil of lubricating grade normally utilized in compounding grease compositions. Suitable base oils include refined, unrefined or semi-refined paraffinic, naphthenic or asphaltic base mineral oils having viscosities of from 50 SSU at 100 F to 300 SSU at 210 F; synthetic hydrocarbon oils such as oligomerized alpha-olefins and oils derived from coal products; and synthetic oils such as aklylene polymers, alkylene oxide-type polymers, polyalkylene glycols, silicone polymers, polyethers, phosphate esters, dicarboxylic acid esters and pentaerythritol esters. The above oils may be used individually or in mixtures thereof, wherever miscible or made so by the use of solvents. Of the aforementioned base oils, mineral lubrieating oils having viscosities of about 150 to 2,500 SSU at F are especially preferred.

In addition to the additive combination hereinbefore described, other additives known to the art to perform a particular function or functions may optionally be included in the present compositions.

For example, in applications wherein extreme loading might be encountered, extreme-pressure agents such as molybdenum disulfide, amorphous antimony sulfides (e.g., antimony trisulfide, antimony tetrasultide, antimony pentasulfide or mixtures thereof), metal carbonates (e.g., calcium carbonate or lead carbonate), esters of phosphorous acids, neutral aromatic sulfur compounds, selenides, sulfurized fatty oils or esters, sulfurized long-chain olefins and the like can be favorably employed to augment the load-carrying properties of the present compositions.

Other additives which can be suitably incorporated into the present compositions include anticorrosion agents, such as, disodium sebacate, glyceryl monooleate, sodium sulfonates, sodium or potassium nitrite, aminoand benzo-triazoles, and isostearamides or imidazolines of tetraethylene pentamine; oxidation inhibitors, such as phenyl-alpha-naphthylamine phenyl-betanaphthylamine, diphenylamine, phenothiazine as well as the various analogs and homologs thereof; viscosity index improvers, color stabilizers, foam depressants and the like.

The present greases may be prepared by any suitable means known to the art. One very efficient method of preparation is that which utilizes the so-called direct transfer process." The steps involved in this process may be described briefly as follows: Clay is dispersed in water to form a l-4 percent aqueous dispersion from which the gangue may be separated by sedimentation or centrifuging to obtain a purified dispersion of the clay containing about 10 percent by weight of calcite. The aqueous clay dispersion is then combined with the hydrophobic surfactant and at least part of the mineral oil component, together with sufficient agitation to cause intimate surface contact of the ingredients for the purpose of enabling adsorption of the surfactant upon the surfaces of the clay. The oleophilic clay product associates with the oil and separates from a major proportion of the water. The remaining oil and oleophilic clay product, which is still wet, is heated to a point sufficient to cause substantially all of the water to evaporate. The components are subjected to a high rate of shear, either during water evaporation or subsequent thereto, during which time any remaining desired lubricating oil may be added.

The additives employed in the present composition may be incorporated into the grease at any suitable stage in the aforedescribed process; however, it is preferred that they be incorporated subsequent to water removal at a temperature of about 200 F. The additives can be added directly to the grease forming constituents, either separately or together, but preferably are added as an oil slurry or concentrate to the otherwise finished grease composition. While it is possible to obtain satisfactory results by mere incorporation and homogenizing, it is preferred that the grease composition so modified be subjected to a high rate of shear to insure uniform dispersion of the respective additives throughout the grease product.

The invention will now be further described by means of the following examples:

EXAMPLE I In order to demonstrate the unique interaction of zinc dialkyl naphthalene sulfonate with carboxylic acid EXAMPLE 2 In order to further demonstrate the excellent properties of the present compositions, a grease composition esters and zinc naphthenate in clay-thickened greases, 5 prepared in accordance with the invention (Grease F) a series of compositions comprising a base grease conwas compared to three commercially available greases taining each of the above-mentioned additives individby means of the tests indicated in Table II. While the ually were compared to a composition containing an exact compositions of the commercial greases are not equivalent concentration of the combined additives in known, they are known to be fully formulated finished the same base grease by means of the test procedures 10 products employed in applications similar to these for set forth in the Table l. The base grease used in this which the present greases are suited. comparison comprised a mineral lubricating oil having TABLE II a viscosity of about 95 SSU at 210 F thickened with 6.7 percent by weight hectorite clay which was water- P P Grease cial X cial Y cial Z proofed with 4.5 percent by weight of an ammoamide formed from tall oil fatty acids and a mixture of poly- Penetration th I I h b f d d d (ASTM D-2l7) e y e ne po yammes as ere n e ore escri e an Unwmked 359 316 308 329 contained 1.0 percent by weight antimony trisulfide, a 60 360 320 322 335 stro es 1.0 percent by weight phenyl-alph a-naphthylamine and Corrosion 1.8 percent by weight sodium nitrite. These conven- (ASTM 0-1743 tional additives were included in the base grease to sfg make it suitable for running the Timken Extreme Pres- Test 20 sure (E.P.) Test and to demonstrate compatibility of 3 the present additive combination with conventional adg mm 034 61 0,71 038 ditives. yna e. o H

TABLE I Timken Zinc dialkyl E.P. test 3 naphthalene Carboxylic Zinc Roll sulfonate, acid ester, naphthenate, Pass, Fail, neck Grease percent wt. percent wt. percent wt. lhs. lbs. Dynamic corrosion test test 5 so 1 cycle-fail o, 9 do. 7,9 60 dO 9,9 4eycle-fail 7,9 30 5 cycle plus 2 static-fail. 6, 4 60 5 cycle plus 2 static-pass 1, 2

1 NASULZS. 2 Butyl stearate. 3 This test is described in ASTM Bulletin 228, February 1958. 4 This test is designed to measure the corrosion resistance characteristics of lubricating greases. The equi ment employed in this test is a simulated automotive wheel bearing assembly similar to that described in STM D-1263. In this test the spindle and inside of the hub are coated with a light coating of the test grease while the inner and outer bearings are packed with a conventional grease. 55 ml. of dilute synthetic sea water is injected in the hub which is then rotated at 660 r.p.m. for 6 hrs. at a temperature of about 160 F. after which it is allowed to remain in a static condition for 18 hrs. (this comprises one cycle). At the end of each cycle the hub and spindle assembly are examined for corrosion, and ii rated passing, the cycle is repeated with a fresh injection of sea Water. Test results are reported as the number of cycles required until bearing failure occurs, i.e., the bearing is so badly corroded it must be replaced.

5 This test approximate conditions prevalent in the roll neck bearings of a 4-high reversing hot strip mill used in rolling steel and is designed to measure the lubricity of a grease. In this test a thin layer of grease is spread on a solid steel journal about 3% inches by of an inch in diameter which is in contact with the surface of a No. 09074 Timken tapered roller bearing. This assembly is placed in a test chamber [or 100 hrs. at a temperature of 350 F. At the end of this period the bearing is pressed ed the journal, examined and rated from 1 (excellent) to 10 (very poor) on the basis of the condition of the lubricant film on the journal and the ease or difficulty in removing the bearings from the journal.

The data presented in Table I show that Greast E Corrosion 5 y 1 Fy 2 Fy 2 Fy t th th t pass fail fail fail con alf llllg e ree componen a i tive com ina ion Mommy Test: of the invention is substantially superior to Greases A, Na.) 1 case 1 psi, B and C containing the additives individually in respect grams/Sm Q04 om M3 M5 to both corrosion and lubricity properties, and is likewise superior to Grease D containing a combination of two of the additives. From the Timken E.P. test results it is apparent that zinc dialkyl naphthalene sulfonate and zinc naphthenate adversely affect the extreme pressure properties of the base grease; however, when used in conjunction with the ester component exhibit no such adverse effects. Thus, it is evident that the zinc dialkyl naphthalene sulfonate, carboxylic acid ester Contained 2.0 wt zinc dinonylnaphthalene sulfonate, 0.75% wt butyl stearate and 2.0% wt zinc naphthenate in a base grease similar to that used in Example I, except that the base grease contained only 4.00% wt. of hectorite clay, 2.40% wt of the aminoainide waterproofing agent, 0.75% wt antimony trisulfide and l.6% wt sodium nitrite. This test is designed to determine the dispensability of a lubricating grease and essentially involves measuring the amount of grease in grams per second which will pass through a standard capillary at a specified pressure and temperature, lbs. and 0 F, respectively. The test procedure is described in detail in the grease test section of Lubrication Engineers Manual," published by U.S. Steel Corporation.

The data shown in Table II indicate that Grease F containing the additive combination of the invention has ASTM corrosion ratings equivalent or superior to the three commercial greases, while its dynamic corrosion properties are quite superior to the commercial products In addition, the grease composition of the in- 7 vention has excellent wear and pumpability properties as indicated by the 4 Ball Wear Test and Mobility test results. (Greases having mobilities of above 0.03 grams/sec are in general comparatively easy to pump, while greases having mobility values of less than 0.01 can be pumped only with great difficulty.)

EXAMPLE 3 Examples of other compositions of the invention include mineral oil or synthetic oil based clay-thickened greases of the type hereinbefore disclosed containing the following additive combinations:

tency by means of a waterproofed montmorillonite clay having incorporated therein (1) from 0.1 to 1.5 percent by weight of a zinc di-C to C alkyl naphthalene sulfonate, (2) from 0.5 to 2.0 percent by weight of an ester of a C to C aliphatic monocarboxylic acid and a C to C aliphatic monohydric alcohol and (3) from 1.0 to 3.0 percent by weight of zinc naphthenate.

2. The grease composition of claim 1 wherein the zinc dialkyl naphthalene sulfonate is zinc dinonyl naphthalene sulfonate.

3. The composition of claim 1 wherein the ester is an ester of a C aliphatic monocarboxylic acid and a C Cone 00110., Cone percent percent percent Grease Zinc dialkyl naphthalene sulfonate wt. Carboxylie acid ester wt. Zine naplithenate w G Zinc dinonyl naphthalene sulfonate-.. 0. 6 n-Octyl stearate 1.0 Zine naphthenate.. 1. 5 H do 1. n-Pentyl palmitate 0.7 do 1. 7 I do 0.7 n-Butyl laurate 1 50 .do 1. 8 J do 0.8 n-Butyl eic0sanate O. (l0 1.. 2. 5 K do 0.9 Ethyl pa1mitate 2.0 H.110 1.0

It is understood that the foregoing examples are given for illustrative purposes only; therefore, the invention in its broader aspects should not be limited thereto.

We claim as our invention:

1. A grease composition consisting essentially of a major amount of lubricating oil gelled to grease consis- 

2. The grease composition of claim 1 wherein the zinc dialkyl naphthalene sulfonate is zinc dinonyl naphthalene sulfonate.
 3. The composition of claim 1 wherein the ester is an ester of a C16-18 aliphatic monocarboxylic acid and a C1 to C8 aliphatic monohydric alcohol.
 4. The composition of claim 2 wherein the ester is butyl stearate.
 5. The composition of claim 4 wherein the lubricating oil is a mineral lubricating oil having a viscosity of from 150 to 2,500 SSU at 100* F. 